One flight crosses many borders. Whose emissions are they?

Domestic aviation sits inside national climate targets. International flights do not — a Lagos→London flight belongs to no single country's books. To stop those emissions falling through the cracks, ICAO built CORSIA: the Carbon Offsetting and Reduction Scheme for International Aviation.

CORSIA's promise is carbon-neutral growth: airlines may keep flying, but emissions above a baseline must be cancelled out — either by buying eligible emissions units (offsets) or by using cleaner fuel.